New England Clam Chowder

1 1/2 c. butter or margarine
3/4 c. diced onions
2/3 c. diced celery
1/2 c. all-purpose flour
4 c. hot milk
3 c. clam juice
3/4 c. diced green pepper, if desired
1/8 tsp. white pepper
1/8 tsp. ground thyme, or to taste
Salt to taste
1 c. diced, cooked potatoes
2 c. chopped fresh clams or 2 cans (6 1/2 oz. each) canned clams


Heat butter in large saucepot and saute onions and celery until tender. Add flour; cook and stir 10 minutes. Gradually add hot milk, stirring with a whisk until thickened and smooth. Add clam juice and simmer 15 minutes. Add clams and green peppers, if desired, white pepper, thyme, salt to taste and potatoes. Cook 10 minutes longer.